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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Genetic investigations of oomycetes associated with marine algae

Fletcher, Kyle January 2015 (has links)
This thesis aims to initially define the present knowledge of pathogens which infect algae, highlighting the potential economic significance of such pathogens, given the recent rise in algaculture. Focus is given to the oomycetes, a group of organisms which already contain several significant genera of plant (Phytophthora) and animal (Saprolegnia) pathogens, as well as Olpidiopsis; a genus reported to significantly impact algaculture in Asia. Subsequent chapters aim to genetically characterise stramenopiles (specifically oomycetes and hyphochytrids) associated with algae in two ways. Firstly known pathogens of algae, Olpidiopsis feldmanni and Anisolpidium rosenvingei are morphologically diagnosed by microscopy and genetically surveyed at phylogenetically significant loci. Further morphological information on these two pathogens is reported here expanding the current knowledge of these rarely reported organisms. Surprisingly, genetic evidence indicates that Anisolpidium, a uniflagellate genus, belongs to the biflagellate class Oomycota and not the closely related uniflagellate class Hyphochytriomycota, as previously suspected. Morphological and genetic features of these classes are contrasted to justify this molecular interpretation. These first two studies, along with the publically available sequences of algal pathogens are then used to design primers, which enable an oomycete-directed metagenomic survey of brown algae, allowing the investigation of what organisms are associated with these. At present the results of this survey are unreported. Finally a Eurychasma dicksonii transcriptome as well as genomic sequences of other stramenopiles are investigated for the presence of cadherin protein models. At present such models are automatically annotated and reported. This study is the first manual curation of the protein and defines a unique protein family which is presented by the oomycete genera Eurychasma, Pythium, Phytophthora and Albugo as well as the labyrinthulomycete Aurantiochytrium limanicum. The protein model is not reported from other sequenced oomycete genera or photosynthetic stramenopiles.

The chemical ecology and antibacterial activity of the brown alga Halidrys siliquosa and other Scottish seaweeds

Ruchonnet, Diane Astrid January 2007 (has links)
In regard to the more and more restrictive legislations on the use of organotins in antifouling coatings the need for the development of 'environmentally friendly' antifouling formulations becomes urgent. This study was initiated by the screening of the antifouling activity of Scottish algae against marine fouling bacteria aI;ld was followed by an examination ofthe chemical ecology ofthe brown alga Halidrys siliquosa. Of eleven algal species tested, eight exhibited good antifouling activity, confirming marine algae as a potential source for the development ofnovel antifouling formulations. H. siliquosa crude extracts tested at concentrations equivalent to whole algal tissue inhibited bacterial growth, with bacteria isolated from the surface orH. siliquosa being less sensitive to the extracts compared to bacteria isolated from stones and open seawater. This suggested for the first time that bacteria associated with the surface of the seaweed had evolved some kind of resistance to the plant antimicrobial activity. Characterisation of the active components using NMR spectroscopy showed the activity to be largely associated with the presence of polyunsaturated fatty acids (PUFAs). Examination of purified fractions using GCIMS allowed identification and quantification of PUFAs 18:2, 18:4, 20:4 and 20:5. A separate study, determining minimum inhibitory concentrations of 18:2 and 20:4 against marine fouling bacteria indicated that both acids were present in sufficient concentrations in the plant to inhibit bacterial growth. The presence of PUPAs on the surface of the seaweed could not be demonstrated using a surface dip technique; however, this technique was originally developed for the extraction of non-polar metabolites only. This study suggests that PUFAs produced by H. siliquosa are potentially able to regulate biofouling by means of disrupting the early stage of biofilm development, i.e. bacterial colonisation. However, to confirm this hypothesis, the presence of PUFAs on the surface of the plant' still needs to be demonstrated.

Seaweed biodiversity around the Antarctic Convergence in the South Atlantic

Mystikou, Alexandra January 2015 (has links)
This study focuses on the seaweed biodiversity around the Antarctic Convergence in the South Atlantic. It integrates field work in the Falkland Islands and surrounding regions with algal culturing, molecular techniques, microscopy and morphological identification. Chapter 2 explores the diversity of seaweeds of the south-western Antarctic Peninsula which is poorly studied, contrasting with the substantial knowledge available for the northern parts of the Peninsula. A baseline seaweed species checklist for the southern Adelaide Island and northern Marguerite Bay region is presented here, combining data obtained during a small number of surveys in 1973-5 and a six week intensive diving-based field campaign in 2010-2011. Subantarctic and Antarctic regions remain little studied in their seaweed diversity. Chapter 3 is based upon field collections in the early 1970s and 2007-2013. It is supported by sequencing COI and reports new records of several macroalgal species and an oomycete. Chapter 4 revisits the enigmatic Subantarctic brown alga Cladochroa chnoosporiformis, which had been collected only on one occasion by Carl Skottsberg in 1907 from Port Philomel, West Falkland, resulting in its formal taxonomic description. Within the framework of this study, Cladochroa was rediscovered after 106 years at its type locality, confirming its existence and morphological features as described by Skottsberg. The recollection enabled molecular studies of its phylogenetic placement by DNA sequencing, suggesting that C. chnoosporiformis is conspecific with Utriculidium durvillei. In Chapter 5, DNA barcoding was applied to both seaweed tissue samples taken while preparing herbarium specimens during 2 expeditions to the Falkland Islands, and to live macroalgal isolates obtained from substratum samples using the Germling Emergence Method. In several cases, this enabled detection of previously unsequenced or undescribed taxa, respectively. The potential and challenges of applying DNA barcoding for cataloguing the biodiversity of remote bioregions such as the Falklands are discussed.

Characterization and nutritional study of the heterotrophic bacteria from marine benthic algae.

January 1977 (has links)
Miu-kuen Kong. / Thesis (M. Ph.)--Chinese University of Hong Kong. / Bibliography: leaves 164-186.

Hydrodynamic performance of seaweed farms : an experimental study at seaweed blade scale

Vettori, Davide January 2016 (has links)
No description available.

Spatial variation on tropical rocky shores : the role of herbivory and disturbance /

Hutchinson, Neil. January 1999 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 220-255).

Taxonomy and morphological variation of the genus Ceramium (Rhodophyta, Ceramiales) in Hawaii

Meneses, M. Isabel January 1990 (has links)
Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references. / Microfiche. / xx, 412 leaves, bound ill. 29 cm

Marine algal chemistry

Woolard, Frank January 1977 (has links)
Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1977. / Includes bibliographies. / I. Halogenated constituents of Chondrococcus hornemanni (Mertens) Schmitz.--II. Halogenated constituents of Asparagopsis taxiformis (Delile) trev.--III. Studies on the biogenesis of the dictyopterene hydrocarbons and sulfur compounds. / Microfiche.

Odoriferous constituents of Dictyopteris

Pettus, John Anthony January 1971 (has links)
Typescript. / Thesis (Ph. D.)--University of Hawaii, 1971. / Bibliography: leaves [217]-219. / xvi, 219 l illus., graphs, tables

Eutrophication and excessive macroalgal growth in Lake Macquarie, New South Wales /

Nicholls, David John. January 1999 (has links)
Thesis (M. Sc.)--University of New South Wales, 1999. / Also available online.

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